Speedy chocolate sauce

I recently made the fudgey All-American Chocolate cake but was in too much of a hurry to eat it to wait for it to cool. And so I made a speedy, no cook, chocolate sauce to pour over and served it warm, like a brownie with ice cream.

Though I have given a stand alone recipe here, in truth what I did was make up the full volume of cocoa and water needed for the recipe, and then just used half to make one cake - I was trying to be a good girl! - and the other half to make up the sauce!